Why I can't find my mesh in menu?
You can't find it in the menu because you didn't add it to the menu. Menus don't automatically pick up new entries based on the class properties, you have to write code to add them:

import bpy

def add_menu_item(self, context):
    self.layout.label("Added this line")
    self.layout.operator("mesh.tree_add")

bpy.types.INFO_MT_mesh_add.append(add_menu_item)